High-speed craft

ABSTRACT

A high-speed craft comprises a hull (1), lifting wings (2) with sponsons (3), and a tail fin assembly including a vertical keel (5) and a stabilizer (6) having an inverted-V configuration and rotatably mounted about a vertical axis (7), driven by a steering gear (13,15). In turning the craft, the forces acting on half-wings of the stabilizer (6) generate a moment making the craft heel to the inner side of the bend, whereby the transverse component of the aerodynamic lift opposes to the lateral drift caused by centrifugal forces acting on the craft.

FIELD OF THE INVENTION

The invention relates to ship building and more specifically, tohigh-speed craft.

BACKGROUND OF THE INVENTION

At high speed, the hull of a vehicle such as the high-speed craft isknown to be acted upon by significant aerodynamic forces. In a number ofcases, provided aerodynamic surfaces are incorporated in the hull of thehigh-speed craft, these forces tend to balance out, partially or fully,the weight of the hull. This pattern of motion allows a noticeabledecrease in the specific power of the craft due to its reduced drag.

These effects that are enhanced by the influence of the water surface("ground") occur at sufficiently high velocities: generally above 10 to12 Fr_(v) (which corresponds to 110-120 km/h for a craft of 1000 kgdisplacement). At such speeds, it involves certain difficulties toprovide both longitudinal and lateral stability of the craft, especiallywhen manoeuvring. It is due to the fact, that if sudden perturbationsoccur such as waves, gusts of wind, the craft may lose contact withwater, take off from the surface, and capsize. When manoeuvring at suchspeeds, the craft is acted upon by significant centrifugal forces whichmay disturb the lateral stability of the craft and result in capsizing,or else, if the area of the steering surfaces is not sufficient, thecraft becomes essentially uncontrollable. These circumstances require adeveloped tail fin assembly, the optimum configuration of the tail finsfor such high-speed craft being either T- or V-shape (N. I. Belayin,"Ekranoplany", 1977, Sudostroenie/Leningrad/, pp. 187-195).

One known high-speed vessel is a ground-effect craft comprising a hullwith a T-shaped tail fin assembly, lifting wings with sponsons, anengine with a propulsion unit, and a steering gear (N. I. Belavin,"Ekranoplany", 1977, Sudoestroenie (Leningrad), pp. 96-99; DE, A,1234539, U.S. Pat. No. 3,190,582). The tail fin assembly of such craftincludes a vertical fin with a portion thereof being made rotatableabout the vertical axis and connected to the steering gear, and astabilizer with a pair of straight (zero-V) half-wings, the stabilizerbeing secured to the stationary portion of the fin.

One disadvantage of this craft is its poor maneuverability when movingover the water surface. It manifests itself in the fact that in order tomake a turn of a specified (small) radius, the craft has either tochange the travel conditions and to increase the clearance or tosubstantially reduce the speed and contact the water surface. Withincreased clearance height, which is in itself an uneconomical andhard-to-control procedure, a heel has to be provided which is inwardrelative to the turn, this heeling being achieved by means of anadditional control system and additional controls, i.e. ailerons(winglets). The additional controls involve great difficulties insteering the craft and, what is more, making the control inefficientwhen the craft moves at a low height. As a result, even thoughadditional control members are provided, the steering of the craft, whenit moves at a low clearance height above the water surface ("ground") ismade difficult, because we fail to provide an effective counteractionagainst the centrifugal forces developed when maneuvering the craft.

DISCLOSURE OF THE INVENTION

The principal object of the present invention is to provide a high-speedcraft with a tail fin assembly designed such that it improvesmaneuverability of the craft as it moves at a high speed, without thenecessity to add extra control members.

With this principal object in view, there is provided a high speed craftcomprising a hull, lifting wings with sponsons, an engine, a steeringgear, and a tail fin assembly including a vertical keel and a stabilizerwith a pair of half-wings, wherein, according to the invention, thestabilizer is mounted rotatably about the vertical axis, has aninverted-V configuration, and is connected with the steering gear.

Owing to this realization of the stabilizer, as the craft is turned, aheeling force directed towards the turn is generated on the innerhalf-wing (relative to the turn), while the lift on the outer half-wingis increased. As a result, a heeling moment acts on the tail finassembly, and hence on the entire craft, which provides the requiredinward heel, whereby a lateral component of the aerodynamic lift exertedon the craft is opposed to the lateral drift generated by centrifugalforces, thus improving the maneuverability of the craft, allowing itsturn on a specified radius at a small height above the water surface,when moving at normal speed.

It is advisable that the stabilizer be of the swept type.

This allows a sternward shift of the lift resultant and an increasedlength of the stabilizer arm, thus substantially improving the craftstability in motion.

If the vertical keel is rotatably mounted about the vertical axis andconnected with the steering gear, it is preferred that the stabilizer berigidly attached to the vertical keel.

Also the vertical keel may have a cavity inside its bottom portion toreceive the above-water part of the outboard engine.

If it is only one section of the vertical keel that is rotatable aboutthe vertical axis and connected with the steering gear, the stabilizeris preferably attached to this rotary section of the vertical keel.

It is also advisable that the rotary section of the vertical keel have acavity in its bottom part to receive the outboard engine.

The arrangement of the outboard engine inside the vertical keel (or itsrotary section) causes the aerodynamic drag of the engine to besubstantially reduced, simultaneously improving the operating conditionsof the stabilizer and protecting the engine from spray.

The craft with an outboard engine also may have the rotary section ofthe vertical keel located above the engine.

In this case, a reduced aerodynamic drag is likewise achieved, alsoproviding a convenient maintenance of the engine.

According to one embodiment of the invention, the vertical keel includestwo elements arranged in symmetry about the center line of the craft.

This results in a more efficient operation of the keel and consequentlyimproves manoeuvrability of the craft due to removal of the keelelements out of the wake zone which is characterized by reducedvelocities.

Here the elements of the vertical keel are preferably positioned at anangle to the center line of the craft.

This enables the heeling moment developed in turning to be optimized.

In an outboard-engine craft, the elements of the vertical keel may besecured to the sides of the engine.

Such arrangement of the keel elements makes the engine readilyaccessible and cases its maintenence.

To increase aerodynamic efficiency of the tail fin assembly and toreduce its weight/size characteristics, the stabilizer may be mounted onthe hull and the element of the vertical keel may be attached to thehalf-wings of the stabilizer.

In case the craft has an outboard engine provided with an aerodynamicfairing, it is advisable that the stabilizer be mounted on the fairingand the elements of the vertical keel be secured to the half-wings ofthe stabilizer.

This aids in a minimized aerodynamic drag of the craft, especially withthe helmsman in a lying or reclining position.

To provide an easier access to the outboard engine, the stabilizersection in the vicinity of the center line of the craft may befabricated of a transparent material.

Both the outboard and the inboard engine may be made still moreaccessible by means of a longitudinal slot provided in the stabilizerand extending at the interface of the elements of the vertical keel.

According to one of the embodiments of the invention, the stabilizerincludes an additional member interposed between the half-wings of thestabilizer.

Such design of the stabilizer ensures its rigid construction and,primarily, prevents the vibrational instability of the craft.

In this case, in order to increase the static stability of the craft andto displace its aerodynamic center more forward location, which isfavorable for the craft stability, and also to provide an easier accessto the engine, the chord of the additional element of the stabilizer isshorter than the half-wing chord at the interface of the additionalelement of the stabilizer and each of its half-wings.

In case of an inboard engine fitted on the craft, it is preferred thatthe craft be equipped with a hydrodynamic rudder connected with thestabilizer.

This gives a significant improvement of the craft manoeuvrability over awide range of velocities.

The invention is further illustrated by a detailed description of itsembodiments with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a side view of a high-speed craft according to oneembodiment of the invention;

FIG. 2 is a sectional view taken along the line II--II of FIG. 1;

FIG. 3 is a side view of a high-speed craft, according to anotherembodiment of the invention;

FIG. 4 is a side view of a high-speed craft, according to still anotherembodiment of the invention;

FIG. 5 is a front view of a high-speed craft, according to still anotherembodiment of the invention, partly cutaway;

FIG. 6 is a front view of a high-speed craft, according to yet anotherembodiment of the invention;

FIG. 7 is a side view of a high-speed craft, according to yet anotherembodiment of the invention;

FIG. 8 shows a front view of a high-speed craft, according to yetanother embodiment of the invention;

FIG. 9 is a front view of a high-speed craft, according to a furtherembodiment of the invention;

FIG. 10 is a plan view of the craft shown in FIG. 9;

FIG. 11 is a side view of a high-speed craft, according to a furtherembodiment of the invention; and

FIG. 12 is a graphic representation of forces acting on the proposedhigh-speed craft in turning.

BEST MODE TO CARRY OUT THE INVENTION

The proposed high-speed craft comprises a hull 1 (FIG. 1) formed by anelongated streamlined body, lifting wings 2 provided with sponsons 3 andsecured to the sides of the hull 1, and an engine 4, such as an outboardmotor, and a tail fin assembly consisting of a vertical keel 5 and astabilizer 6, both the engine and the fin assembly being mounted on thestern of the craft, the stabilizer consisting of two half-wings 6a and6b (FIG. 2) arranged in an inverted-V configuration. The stabilizer 6 isrigidly attached to the vertical keel 5 which is rotatably mounted abouta vertical, or near-vertical, axis 7 (FIG. 1) indicated symbolically bya dash-dot line. The vertical keel 5 has a cavity 8 provided in itsbottom section and housing the outboard engine 4. The thickness of thekeel 5 is 15 to 17% of its chord length, making it possible to cowl theengine 4 and to provide the required airfoil surface of the keel. Toensure stability of the craft at anchorage or in slow motion (inhull-borne conditions) and to minimize the after draught, the bottomsection of the vertical keel 5 also encloses a buoyancy module 9composed, say, of foam.

The outboard engine 4 is secured to a transom 10 of the hull 1 by meansof an attachment fitting 11 and is connected with the vertical keel 5 byan easily detachable joint 12 (FIG. 2), such as bolts, so that the keelhinge axis 7 (FIG. 1) is at the same time an axis of rotation of theengine 4. The axis of rotation of the engine, however, may fail tocoincide with the hinge axis of the vertical keel 5, necessitating theprovision of an additional device for the keel and engine rotations tobe locked into step. Making both the keel 5 and the outboard engine 4rotatable about the same axis results in a simpler construction of thecraft.

The craft further comprises the steering gear including a steering wheel13 located in a cockpit 14 and tiller ropes 15 for connection of thesteering wheel 13 with the outboard engine 4 and the vertical keel 5through ports 16 in the sides of the hull 1. The tiller ropes 15 rest onsupports 17.

The inverted-V angle of the stabilizer 6 lies within a sufficiently widerange, namely, from 2° to 25°, the preferable range being 10°-20°. Itsmagnitude depends on the specific aerodynamic characteristics of thehigh-speed craft, in particular, the area ratio of the lifting wings 2and the stabilizer 6, the center-of-gravity location of the craft, theV-angle of the wings 2, etc.

In the embodiment of FIGS. 1 and 2, the stabilizer 6 is swept in planview, i.e. the tips of its half-wings 6a and 6b are shifted sternwardsrelative to the points of their attachment to the vertical keel 5.However, this is not the only embodiment of the invention, and otherarrangements of the stabilizer half-wings are possible, such as thatwith the zero sweep. The wing sweep improves the operating conditions ofthe stabilizer and provides a greater arm length, resulting in a betterstability of the craft. Neither does the vertical keel 5 always need tohave the cavity 8 within. In case the hull 1 is sufficiently developedat the stern and its vertical dimension is comparable to that of theengine, the latter may be located below the vertical keel.

FIG. 3 shows another embodiment of the proposed craft differing from theabove by the vertical keel 5 consisting of two parts: a stationarysection 5a and a rotary section 5b rotatable about the axis 7, thestabilizer 6 being rigidly attached to the rotary section 5b of thevertical keel. Making only part of the keel 5 rotary is justified incase of a higher velocity of the craft, when the rotation of even onepart of the vertical keel ensures the manoeuvrability required.Similarly to the design shown in FIGS. 1 and 2, the rotary section 5b ofthe rotary keel 5 is made hollow at bottom, and a cavity 16 receives theoutboard engine 4, resulting in a substantially minimized aerodynamicdrag of the craft, but making it somewhat more difficult to access theengine. In fact, if the ease of maintenance is one of the criticalpoints in the design, the engine 4 may be disposed below the rotarysection 5b of the keel (FIG. 4) which is manufactured essentiallywithout an inner cavity. Such arrangement of the outboard engine 4 ispreferred when the hull 1 is sufficiently high at the stern, fully orpartially protecting the engine from the incident flow.

FIG. 5 shows still another embodiment of the proposed craft, in whichthe vertical keel consists of two elements 5c and 5d arranged insymmetry about the center line of the craft and secured to the sides ofthe outboard engine 4 by easily detachable joints 19. Here the half-wing6a of the stabilizer is attached to the element 5c, and the half-wing6b, to the element 5d. The attachment of the elements 5c and 5d to thesides of the engine 4 provides an easy access thereto, though somewhatimpairing the aerodynamic drag of the craft. In addition, the design ofFIG. 5 slightly reduces the size of the tail fin assembly, facilitatingthe control. The elements 5c and 5d form an angle with the center lineof the craft, so that the angle formed by each of these elements 5c and5d and the respective half-wings 6a and 6b of the stabilizer is close toright angles (90°). The positioning of the elements 5c and 5d of thekeel at an angle to the center line of the craft, in the first place,improves aerodynamic operating conditions of the vertical keel, leadingto an undisturbed flow around it, and secondly, it simplifies theprocess of manufacturing the tail assembly, resulting in a strong andrigid stabilizer. The tilt angle of the keel elements 5c and 5d to thecenter line of the craft is generally within 30°. When the tilt angleexceeds this value, the aerodynamic effect of the vertical keel drops.

To facilitate the maintenance of the outboard engine 4, particularlywith small vertical dimensions of the keel elements 5c and 5d, theportions of the half-wings 6a and 6b disposed between the keel elements5c and 5d in the vicinity of the center line of the craft are made of atransparent material such as plexiglas. Another means of easing theaccess to the outboard engine is a longitudinal slot 20 provided in thestabilizer 6 (FIG. 6).

The vertical keel elements 5c and 5d may also be attached to a speciallyprovided rotary member rather than to the outboard engine. Thisconstruction, however, is much more complicated than those representedin FIGS. 5 and 6, making its use only justified with the inboard engine.

Provided the hull 1 of the craft is sufficiently developed and itsvertical dimension is comparable to that of the above-water part of theoutboard engine 4, and the aerodynamic configuration of the craft issuch that a small wash occurs in the stern flow, the tail fin assemblyof the craft is preferably realized in accordance with FIGS. 7 and 8. Asshown in FIG. 7, the stabilizer 6 is mounted directly on the hull and isadapted to be rotatable about the vertical axis 7. On the other hand, ifthe outboard engine 4 is provided with an aerodynamic fairing 21 (FIG.8), the stabilizer 6 is mounted on the fairing 21. In both cases, theelements 5c and 5d of the vertical keel are secured to the tips of thehalf-wings 6a and 6b, respectively, of the stabilizer.

According to FIG. 9, the stabilizer further comprises an additionalmember 6c interposed between the half-wings 6a and 6b. Such design ofthe stabilizer contributes to prevention of vibrational instability ofthe craft. Despite the fact that the stabilizer with the additionalmember, according to FIG. 9, is attached to the vertical keel consistingof the two elements 5c and 5d, it is evident that such stabilizer may bemounted on a one-piece keel located at the centre line of the craft, onthe craft hull, or on the fairing of the outboard engine, i.e. in thedesigns illustrated in FIGS. 1, 3, 4, 7 and 8. Now, if the keel isformed by two elements 5c and 5d (FIGS. 7, 8, 9), the chord of theadditional member 6c of the stabilizer on a section 22 (FIG. 10) whereit joins either of the half-wings 6a and 6b, is shorter than the chordof these half-wings. This enables the static stability of the craft tobe improved, when necessary, and the engine to be more easily accessed.Moreover, this design of the additional member 6c of the stabilizerpermits the aerodynamic center to be shifted, in height, towards the bowof the craft.

In accordance with FIG. 11, the engine 4 is mounted inside the hull 1.The craft has an additional hydrodynamic rudder 23 located in the sternportion of the bottom and connected with the steering gear. To simplifythe construction of the craft, the hydrodynamic rudder stock coincideswith the axis 7 of rotation of the vertical keel 5 and the stabilizer 6.

When the craft is moving on water, it is acted upon by an aerodynamiclift P_(c) (FIG. 12) which is the sum of the aerodynamic lift P_(k)acting on the main wings 2, and the aerodynamic lifts P_(a) and P_(b)acting on the half-wings 6a and 6b, respectively. After the craft hasbeen accelerated to a certain speed, such as 8-12 Fr_(v), theaerodynamic lift P_(c) reaches the weight of the craft, and the planingsurfaces of the hull 1 and the sponsons 3 are brought out of engagementwith the water. But the propeller of the engine 4 remains submerged,providing the required velocity. The outboard engine 4 cowled in thevertical keel 5 presents the minimum resistance to the motion, thusminimizing the induced drag of the entire craft. The turn of thesteering wheel 13 (FIG. 1) causes the rotation of the vertical keel 5 orits rotary section 5b (FIGS. 3, 4) and of the stabilizer 6. Now, becausethe stabilizer 6 has an inverted-V configuration, a sinking force P_(T)(FIG. 12) is generated on its half-wing which is on the inner side ofthe bend, such as the right-hand half-wing 6a when turning right, andthe lift P_(b) acting on the outer half-wing 6b is increased.Consequently, the tail assembly and hence, the entire craft is subjectedto a moment M of high magnitude, which makes the craft heel tostarboard. Now, the centrifugal forcee R_(c) generated in turning thecraft comes to be balanced out by the transverse component P_(z) of theaerodynamic lift P_(c), thus improving lateral stability whenmaneuvering, and allowing the turns of a sufficiently small radius to beperformed by the helmsman without slowing down. This heeling moment Menables the inner surface of the right-hand sponson 3 to be brought intoengagement with the water, developing a significant hydrodynamic forceopposed to the lateral drift.

When the craft follows the straight course and is subjected to a strongcross wind, the known craft such as those described in theaforementioned references, deviate from the course or heel to leewardside. The proposed craft, owing to the inverted-V configuration of thestabilizer, especially in combination with the inverted-V configurationof the lifting wings, is free from this disadvantage, since a sinkingforce is produced on its windward wing 2 as well as on the windwardhalf-wing of the stabilizer, such as the half-wing 6a, while anadditional lift is developed on the leeward half-wing 6b. The heelingmoment generated thereby and opposing to the wind tends to compensatefor most of the heeling moment generated due to the forces appearing onthe vertical keel and other elements of the craft.

In the craft designs shown in FIGS. 7 and 8, where the elements 5c and5d of the vertical keel are mounted on the stabilizer 6 at an angle tothe center line of the craft, the heeling force acts not only on thestabilizer half-wing on the inner side of the bend, such as thehalf-wing 6a, but also on the respective element 5c of the verticalkeel. This further increases the heeling moment, consequently improvingmaneuverability of the craft. Moreover, the elements 5c and 5d of thevertical keel of the craft shown in FIGS. 7 and 8 function asaerodynamic end plates preventing the air flow from the pressure face ofthe stabilizer 6 to its suction face and enhancing the stabilizingeffect.

The optimum value of the inward heel and consequently, the requiredlateral stability and manoeuvrability of the craft, are provided by anappropriate choise of areas of the elements of the tail fin assembly andthe lifting wings, of their angles of incidence V-angle of thestabilizer, the center-of-gravity location of the craft, etc., whendesigning the craft.

In case of the inboard engine provided on the craft, the water ruddersurface area is further taken account of.

INDUSTRIAL APPLICATION

The invention can be used in a wide range of sports, racing, pleasureboats, particularly in aerodynamic-relief craft (i.e. those having theirhull weight, when moving at high velocities, balanced out not only byhydrostatic and hydrodynamic forces, but also by aerodynamic forces) andin ground-effect craft. The aerodynamic-relief craft may include raceplaning boats and scooters of the classes such as R1, R2, OA, OB, OC,OD, ON, etc.

We claim:
 1. A high-speed craft comprising a hull (1), lifting wings (2)with sponsons (3), an engine (4), a steering gear and a tail finassembly including a vertical keel (5) and a stabilizer (6) comprising apair of half-wings (6a, 6b), wherein the stabilizer (6) is connected tothe steering gear rotatably mounted about a vertical axis (7), and thepair of half-wings is mounted in an inverted-V configuration.
 2. A craftas claimed in claim 1, wherein the half-wings (6a, 6b) of the stabilizer(6) are swept wings.
 3. A craft as claimed in claims 1 or 2 wherein thevertical keel (5) is rotatable about the vertical axis (7) and connectedwith the steering gear, wherein the stabilizer (6) is rigidly attachedto the vertical keel (5).
 4. A craft as claimed in claim 3, wherein theengine (4) is an outboard engine, and the vertical keel (5) has a cavity(8) provided in its bottom part, and the engine (4) is housed insidesaid cavity (8).
 5. A craft as claimed in claim 3, wherein the verticalkeel (5) includes a pair of elements (5c, 5d) arranged symmetricallyabout the center line of the craft to support the stabilizer.
 6. A craftas claimed in claim 5, wherein the elements (5c, 5d) of the verticalkeel (5) are mounted at an angle to the center line of the craft.
 7. Acraft as claimed in claim 6, wherein the engine (4) is an outboardengine wherein the elements (5c, 5d) of the vertical keel (5) aresecured to the sides of the engine (4).
 8. A craft as claimed in claim6, wherein the elements (5c, 5d) of the vertical keel (5) are mounted onthe hull and secured to the half-wings (6a, 6b) of the stabilizer (6).9. A craft as claimed in claim 6, wherein the engine (4) is an outboardengine and is provided with an aerodynamic fairing (21), wherein thestabilizer (6) is mounted on the fairing (21), and the elements (5c, 5d)of the vertical keel (5) are secured to half-wings (6a, 6b) of thestabilizer (6).
 10. A craft as claimed in claim 6, wherein the engine isan outboard engine, wherein a portion of the stabilizer (6) in thevicinity of the center line of the craft is made of a transparentmaterial.
 11. A craft as claimed in claim 6, wherein the stabilizer (6)comprises a longitudinal slot (20) disposed between the elements (5c,5d) of the vertical keel (5).
 12. A craft as claimed in claim 5, whereinthe engine (4) is an outboard engine wherein the elements (5c, 5d) ofthe vertical keel (5) are secured to the sides of the engine (4).
 13. Acraft as claimed in claim 5, wherein the elements (5c, 5d) of thevertical keel (5) are mounted on the hull and secured to the half-wings(6a, 6b) of the stabilizer (6).
 14. A craft as claimed in claim 5,wherein the engine (4) is an outboard engine and is provided with anaerodynamic fairing (21), wherein the stabilizer (6) is mounted on thefairing (21), and the elements (5c, 5d) of the vertical keel (5) aresecured to half-wings (6a, 6b) of the stabilizer (6).
 15. A craft asclaimed in claim 5, wherein the engine is an outboard engine, wherein aportion of the stabilizer (6) in the vicinity of the center line of thecraft is made of a transparent material.
 16. A craft as claimed in claim5, wherein the stabilizer (6) comprises a longitudinal slot (20)disposed between the elements (5c, 5d) of the vertical keel (5).
 17. Acraft as claimed in claims 1 or 2, wherein the stabilizer (6) includesan additional member (6c) interposed between the half-wings (6a, 6b).18. A craft as claimed in claim 17, wherein the additional member (6c)of the stabilizer (6) joins each of the half-wings (6a, 6b) and thechord of the additional member (6c) is shorter than the chords of thehalf-wings (6a, 6b).
 19. A craft as claimed in claims 1 or 2, whereinthe engine (4) is stationarily mounted, and the craft further includes ahydrodynamic rudder (23) connected with the stabilizer (6).
 20. A craftas claimed in claims 1 or 2, wherein a section (5b) of the vertical keel(5) is connected with the steering gear and is rotatable about thevertical axis (7); the stabilizer (6) being rigidly attached to therotatable section (5b) of the vertical keel (5).
 21. A craft as claimedin claim 20, wherein the engine (4) is an outboard engine, and therotary section (5b) of the vertical keel (5) has a cavity (18), providedin its bottom part, and the engine (4) is housed within said cavity(18).
 22. A craft as claimed in claim 20, wherein the engine (4) is anoutboard engine, and the rotatable section (5b) of the vertical keel (5)is located above the engine (4).